Issue 35

S. Boljanović et alii, Frattura ed Integrità Strutturale, 35 (2016) 313-321; DOI: 10.3221/IGF-ESIS.35.36 317 N UMERICAL RESULTS o illustrate the efficiency of the computational model for the fatigue failure analysis of lug with either semi- elliptical crack or through-the-thickness crack, a few numerical examples are presented in this Section. The strength of lug is here investigated through the stress analysis, the residual life estimation and the crack path simulation. The fatigue life calculation of through-the-thickness crack In the first Section, the residual strength of the pin-loaded lug with through-the-thickness crack (Fig.1, case 2) is examined. The lug, subjected to axial cyclic loading with constant amplitude (a far-field maximum stress S max = 41.38 MPa), has diameter of a hole 2 r =38.1 mm and initial crack length b 0 = 0.635 mm [21]. Geometry sizes and relevant stress ratios are shown in Tab. 1. The cracked lug is made of 7075 T6 Al Alloy, and the following material characteristics are assumed: C B = 2.55  10 -10 , m B = 3.06 [22]. Using the above geometry sizes, fatigue data and loading conditions, the stress intensity factor for the lug with through- the-thickness crack is calculated by applying Eq.(14) and appropriate relationships discussed in Ref. [16, 18], then thanks to Eqs.(2a) and (2b), the number of loading cycles up to failure is evaluated. Figs. 2a, 2b and 2c show the computed results for lug configuration with through-the-thickness crack. In the same Figures, the estimations are compared with available experimental results [21]. It can be deducted from Fig.2 that the calculations and experimental data are in a good correlation. 0 5 10 15 20 25 30 35 0 20 40 60 80 100 120 140 N [cycles] (x10 3 ) b [m] (x10 -3 ) Calculated curve Experiment 1 Experiment 2 0 5 10 15 20 25 0 20 40 60 80 100 N [cycles] (x10 3 ) b [m] (x10 -3 ) Calculated curve Experiment 1 Experiment 2 0 2 4 6 8 0 5 10 15 20 N [cycles] (x10 3 ) b [m] (x10 -3 ) Calculated curve Experiment 1 Experiment 2 (a) (b) (c) Figure 2 : Crack length versus number of loading cycles for the pin-loaded lug with through-the-thickness crack emanating from a hole: (a) Experiment 1-ABPLC84, Experiment 2-ABPLC91; (b) Experiment 1-ABPLC47, Experiment 2-ABPLC94; (c) Experiment 1- ABPLC63, Experiment 2-ABPLC62. Experimental results for through-the-thickness crack configuration from Ref. [21]. Lug ID 2w 10 -3 (m) 2t 10 -3 (m) R ABPLC84 ABPLC91 114.3 12.7 0.5 ABPLC47 ABPLC94 85.72 12.7 0.5 ABPLC63 ABPLC62 57.15 12.7 0.1 Table 1 : Geometry sizes of the lug and external loading conditions [21]. T